Fractional distillation process and system control for maximum vapor load

Claim 1

IN A FRACTIONATION PROCESS WHEREIN A FLUID MIXTURE TO BE SEPARATED IS INTRODUCED INTO A FRACTIONATION ZONE, A KETTLE PRODUCT STREAM IS WITHDRAWN FROM THE LOWER REGION OF SAID ZONE A VAPOR STREAM IS WITHDRAWN FROM THE UPPER REGION OF SAID ZONE, SAID VAPOR STREAM IS COOLED TO CONDENSE SAME, A POTION OF THE RESULTING CONDENSATE IS RETURNED TO SAID ZONE AS EXTERNAL REFLUX, AND THE REMAINDER OF SAID CONDENSATE IS REMOVED AS AN OVERHEAD PRODUCT STREAM; A METHOD OF CONTROLLING THE REFLUX TO BE EMPLOYED IN SAID ZONE TO PERMIT A MAXIMUM VAPOR LOAD WHICH COMPRISES ESTABLISHING A FIRST SIGNAL F WHICH IS REPRESENTATIVE OF THE FLOW OF THE FLUID MIXTURE TO SAID ZONE; MEASURING THE COMPOSITION OF THE FEED MIXTURE AND ESTABLISHING A SECOND SIGNAL WHICH IS REPRESENTATIVE OF THE QUANTITY (D/F), WHERE 8D/F) IS THE VOLUME PERCENT IN TH FLUID MIXTURE OF THE COMPONENTS THEREIN TO BE REMOVED FROM SAID ZONE AS SAID OVERHEAD PRODUCT STREAM; MULTIPLYING THE SECOND SIGNAL BY THE FIRST SIGNAL TO ESTABLISH A PRODUCT SIGNLA D; SUBTRACTING THE PRODUCT SIGNAL D FROM A REFERENCE SIGNAL K1 TO ESTABLISH A CONTROL SIGNAL WHICH IS REPRESENTATIVE OF THE MAXIMUM VAPOR LOAD CAPACITY OF SAID ZONE WHICH DOES NOT RESULT IN FLOODING; AND ADJUSTING THE RATE OF FLOW OF SAID EXTERNAL REFLUX IN RESPONSE TO SAID CONTROL SIGNAL.